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How to Measure the Height of a Tree or Object

Indirectly Measuring the Height of an Object can be a challenging task. Many trees are too large to measure with a handy little pocket tape, plus, how do you manage your way through all the branches to get an accurate reading. In this article I’m going to go over how to measure the height of a tree using an Abney level (like a hand level) and a clinometer. The great part about using these tools is they are inexpensive and can be used in many different situations. All the principles below can also be used to measure the height of a building, pole or practically anything you need to measure from the ground. The bad part is that you’ll have to remember the Trigonometry you learned in high school, but don’t worry, I’ll walk you through it so it’ll be a breeze.

For each of these methods of measurement you will need to know how far you are from the base of the tree. This can be determined quickly and easily with a measuring wheel or long measuring tape, preferably an open reel measuring tape. To measure using a measuring wheel, simply roll the wheel as you walk away from the base of the tree. The counter will display the distance you’ve traveled. For using the clinometer it is recommended that you walk at least 1 to 1 and a half the height of the tree.

Next we will need to use our clinometer to find out the angle of elevation to the top of the tree. The clinometer will feature an eye piece for you to look through; this will display the angle of elevation. Keep both eyes open and look at the top of the tree with one eye and through the eye piece on the clinometer with the other eye. The two images will be transposed onto each other. Take note of the angle of elevation. This will be used to determining the height of the tree. It is represented by the letter “A” on the reference picture below. (Please remember that you will need to account for your height unless you want to lie on the ground and determine the angle from there.) Those two measurements are all we need to plug into our equation. Next we’ll use some trigonometry.

The first thing we need to do is to find the tangent of the angle of elevation. The easiest way to find this would be by using a calculator you could also use a table of trigonometric functions. If you are using a calculator push the “TAN” button and enter the angle and then equals, the number now displayed on the screen will be the TAN of the angle. Now multiply that number by the distance you are from the tree. The number you have now is the height of the tree without (without your height). Simply add the distance from the ground to the where you took the measurements (your eye level to the ground in most cases) and this will be the height of the tree.

Some clinometers have an easy feature built in to help estimate height. Clinometers have scales that display percent and distance (most come in feet but some will have meters). With this method you will still need to know your distance from the base of the tree. It is easiest if you move the distance away from the tree that the distance scale on your clinometer is adjusted to. For instance, if it is set at 66, which is the most common, it is suggested that you move 66 feet away from the base of the tree. The next step is too look at the top of the tree the number indicated on your distance scale is the height of the object you are looking at (minus your height). Make sure you add your height to the measurement this can be done by simply looking at the base of the tree now and adding the two numbers together or by a simple height measurement.

If you are working with the percentage scale it is a little harder but still a relatively easy process. First, find out your distance from the tree. (Because the height of the tree is represented by a percentage in comparison to your distance from the tree you will need to be further away from the tree than the height. 1 ½ the height of the tree is recommended.) To find the height of the tree look through the hand level and note the number on the scale, it represents a percentage of the distance that you from the tree. If it reads 100 then the distance you are from the tree is the same as the height of the tree. If it shows 50 than the tree height is half the distance you are from the base of the tree (minus your height). Next add you eye level height to this measurement. If you want to double check this measurement try doing the same steps from multiple points around the tree. If the tree is leaning the measurement will not be as accurate as if it were straight. If you must measure a leaning tree it is better to have the tree leaning to the right or left as opposed to towards or away from your position.

Engineer supply has many tools helping those working in the forestry industry we have provided many instruments to the nation forest service as well as many local, state and national parks across the nation. EngineerSupply looks forward to assisting you with your forestry needs.

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